"I can tell you how good of a father my dad was towards us. He's amazing. He's brought the best out of all of us kids," the son, who did not wish to be named, told Fairfax Media.

"He's just got a massive heart. He's made mistakes, we've accepted it... he's made up for them.

"For everything to be brought back up (is) pretty heartbreaking to be honest."

He said Mr Farnell and his wife, Wendy, were devastated by allegations they had taken their healthy daughter home to Western Australia but left their son Gammy, who has Down syndrome, behind in Thailand with his surrogate mother, Pattharamon Janbua.

The son spoke to Fairfax Media in Bunbury and said that his father and his wife would soon issue a statement outlining their side of the story.

"The statement will cover everything, it will clear everything up," he said. "You aren't going to get any information whatsoever out of any family members until dad and Wendy have made their statement."

The Supreme Court of Western Australia documents detail how the electrician held "secretive meetings" with the girls in a garden shed or at home, where he touched them inappropriately and forced them carry out sexual acts.

Mr Farnell is the father of three grown children, all of whom he shares a close relationship with.

"We all live quite close to each other and we've all got a strong relationship, even my mother, his ex-wife, regardless of all the stuff that's happened in the past, we are all real tight," Mr Farnell's son said.

"He's taken 10 years to get his life back on track and he did and he has done so well and this, this has been shattering."

The son said he and his siblings were frustrated at not being able to discuss their version of the story behind the Gammy surrogacy scandal because Mr Farnell had to follow the right legal processes.

"Right now we just have to follow the legal channels and as frustrating as that is, that's the way it is," he said.

Despite the couple's silence, up to 20 journalists have camped out the front of the Farnells' family home since news of the scandal broke.

RSPCA officers went to their South Bunbury home on Wednesday and removed the family dog, who had been left barking from a side gate for three days.